The present invention relates to a stored-programcontrol switching system and, more particularly, to a decentralized control-type switching system.
Electronic switching systems are generally classified into two types --that is, a centralized control-type and a decentralized control-type. The centralized control-type electronic switching system is, by way of example, disclosed in an article by Masaya Yamauchi, et al., entitled "D-10 Electronic Switching System," in the technical journal Japan Telecommunications Review, July 1971. This switching system is composed of speech path equipment, including switching network, trunk circuit, etc. and central processor to control the speech path equipment, and data of each circuit in the speech path equipment as processed respectively in different means in the central processor.
On the other hand, the decentralized control-type electronic switching system is, by way of example, disclosed in an article by Mats Eklund, et al., entitled "AXE10-System Description," in the technical journal Ericsson Review, No. 2, 1976. The switching system is characterized by a hierarchic division into switching hardware, regional processors and central processors. The control system for the switching system is composed of a regional processor for controlling a speech path switch, another regional processor for controlling a trunk unit, still another regional processor for controlling subscribers' circuits and subscriber concentrating switches, and duplicated central processors, and the data transfer between these plurality of regional processors and one central processor is carried out under the control of the central processor.
However, the above-mentioned centralized-type electronic switching system and decentralized-type electronic switching system had the following shortcomings. Firstly, upon introducing different signaling systems, in order to effect change or addition of a function, in said centralized control-type electronic switching system, it is necessary to execute change or addition of the program in the central processor. Consequently, the change or addition of the function results in effects upon every place in the switching system. Furthermore, in the decentralized control-type electronic switching system also, a plurality of kinds of functions must be achieved in one processor such that processings pertinent to a plurality of signaling systems are carried out in each regional processor or in the central processor, and, therefore, although change or addition of one block of functions can be achieved in each processor, the change or addition would affect a plurality of kinds of functions so that the change or addition of a program was difficult. Secondly, in either type of the above-mentioned switching systems, since the overall control is managed by a single central processor, the central processor must be of highly excellent performance. Thirdly, in either type of the abovereferenced switching systems, since connection and processing of a communication call are effected by means of a single central processor, there is a limit to the processing capability and the expansibility is poor. Fourthly, in either type of the above-mentioned switching systems, since a central processor of highly excellent performance is necessitated, the central processor occupies a large weight of the switching system, especially in the case of a small-sized switching system, and thus, the switching system is uneconomical.